Chapter 24: Human Origins and Evolution Flashcards
define primates. what characteristics do they have that make them different from other mammals?
-"prosimians" = (lemurs, bushbabies) monkey's + apes -nails rather than claws -eyes in front instead of on the side (allowing 3 dimensional vision) -opposable thumbs
from which three pools of information do we gather our information to trace lineage of organisms?
-The fossil record
• The DNA (molecules)
• The physical features (anatomy)
what are included in the “great apes”?
orangutan gorilla chimpanzee humans (we are all part of the same monophyletic group because we are all descendants of a common ancestor)
which member of the “great apes” are the sister group to humans? (closest related)
chimpanzees
we differ in DNA sequence by just 1%!
what is Sahelanthropus tchadensis?
the earliest hominin
- blend of human and chimpanzee skulls
- 7 million years ago was when the split began
what is Australopithecus afarensis?
“Lucy”!
- 3.2 million years ago
- bipedal
- less than 4 feet tall
what is Ardipithecus ramidus?
“Ardi”
- 4.4 million years old
- bipedal on land, quadrupedal in trees
when did hominins go completely bipedal?
somewhere between Lucy and Ardi
“sapiens”
modern
“neanderthanensis”
from Neandertaler
“floresiensis”
from Indonesian island of Flores (known as the “hobbit”)
-adults just over 3 feet tall
“erectus”
upright
“heidelbergensis”
from heidelberg
“ergaster”
working
“rudolfensis”
from Lake Rudolph
“habilis”
nimble, quick, swift
how many mya did the hominin lineage first wander out of africa?
about 2 million years ago
homo eragaster/homo erectus
first hominin to venture out of africa
when did Neanderthals first appear?
- first appeared in fossil record about 600,000 years ago
- disappeared about 30,000 years ago
why do mammals often evolve small body size on islands?
because limited availability of food
what is the “multiregional hypothesis” of human origins?
• Homo ergaster roots
• Migrated out of Africa about 2 mya
• Many separate migrations from different populations
• Modern humans evolved in parallel out of these
different pop’ns.
• Proven incorrect by the Out of Africa theory
what is the “out of africa” hypothesis of human evolution?
• Much more recent move from Africa
• 200,000 ya rather than 2 mya
• Modern humans evolved from H. ergaster (H.
heidelbergensis) while still in Africa
• Then split off to various pop’ns as they continued to
migrate and separate across the region
mitochondrial DNA (mtDNA)
- small circle of DNA about 17,000 base pairs long
- found in every mitochondrion
- much more abundant than nuclear DNA and easier to extract
- no recombination in mtDNA
- all mtDNA is inherited by the mother (allows us to trace mutations because thats the only way genetic changes could arise in this form of DNA)
what is some evidence for/against humans ad neanderthals interbreeding?
- Neanderthal and Modern
did interbreed but the
mtDNA has since been lost.
2. Neanderthal males interbred with Modern females but Neanderthal females did not interbreed with Modern males.
- 600,000 year difference, at
least
define neoteny
when a sexually mature organisms still retains juvenile physical characteristics
what are 4 anatomical factors that must have changed to make the shift from quadrupedal to bipedal possible?
- foramen magnum (hole in base of skull) repositioned so that human skull is balanced directly on the vertebral column
- spine - S -shaped to ensure weight is directly over the pelvis
- legs - legs directly under body, stronger to support weight
- feet - human foot is narrower and has a bigger arch with a larger big toe
what are some selective factors that allowed us to evolve brains which are proportionally too large for our body size?
tool use - manual dexterity, need complex nervous organization
social living - coordination and communication (for example to successfully hunt in groups)
language
what are 4 important modern human features?
- Bipedal locomotion
- Neoteny
- Large brains
- FOXP2 gene (plays important role in development and communication)
what is the percentage of human genetic variation throughout our species?
- about 1 in every 1000 base pairs is different among humans
- level of human variation is 0.1%
- we are not very genetically diverse!!
the human genome consists of approximately how many base pairs?
3 billion
about how many years ago did modern humans cross from Siberia to North america to populate the new world?
15,000 years ago
